NCD questions

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Lars Clausen

Member
Joined 2003
newclassd.com
Finally ....
lm4562.jpg
 
K

kittikun

Member
Joined 2004
discoveryhifi.com
Hi Lars,

It may be a little off topic but I know you could help me. I've just finished Zappulse 2.3 SE few days ago. It sounds excellent. The problem is I used a tube preamp and it has some background noise from the pre. When the noise goes through the module, it's quite annoying at my speaker. If I were to put a resister at the input of the module around 10-20K to reduce the noise, is it OK? Please recommend the proper value.

I also concern about the DC from preamp. Is it wise to put some cap at the input too? If yes, I plan to put 2.2-4.7 mfd at the input of the module for protection.

Last question for NCD topic, Does it sound better than Zappulse 2.3 SE? If yes, in what way does it better? Thanks for your help.

Kittikun:D
 
D

deandob

Member
Joined 2002
Listening impressions???

Hi,

There does not seem to be too many people posting listening impressions for the new NCD amps. I'm interested in the comparison between the pre & post filter feedback setting especially for the dynamics, and a comparison between the UCD (not to say which one is better, just listening differences).

Regards,
Dean
 
soongsc

soongsc

Member
Joined 2005
Re: Listening impressions???

deandob said:
Hi,

There does not seem to be too many people posting listening impressions for the new NCD amps. I'm interested in the comparison between the pre & post filter feedback setting especially for the dynamics, and a comparison between the UCD (not to say which one is better, just listening differences).

Regards,
Dean
Click to expand...

Prefilter feedback is better. Very sensitive to transformer performance. I tried R-core and O-core transformers of the same rating, the O-core presented a more realistic bass.
 
L

Lars Clausen

Member
Joined 2003
newclassd.com
kittikun: I am sorry to be unable to give you advice on products from companies other than my own. I suggest you contact their technical support.

You would find the information you are looking for in the NewClassD cookbook, that can be downloaded from our website. These solutions are designed for NewClassD amplifier modules. Whether the same solutions can be applied with your ZAPpulse is something that can be considered. But unfortunately not something i can give you advice on.

LM4562: My initial testings show that THD data does not improve with this chip compared to LM6172, which actually has very good THD performance, almost comparable to the best i have tested so far (OPA 627).
However the sound may very well be better on LM4562, but i have until now only made functional tests of sound performance, no A/B tests.
 
soongsc

soongsc

Member
Joined 2005
The golden mean said:
Soonngsc; the concept O-core transformer, was unknown to me.
Should this read what we use to call toroid transformer. I guess it should.

o-core
Click to expand...

I think most toroidal transformers have cores a rectangular cross section, this type of core has a round cross section. Probably it's just call the O-core to differentiate itself from the market. However, there do seem to be other reports indicating positive results, that's why I tried it.
 
soongsc

soongsc

Member
Joined 2005
Lars Clausen said:
The round cross section gives O-Cores the lowest possible distance per winding = lowest impedance. I suspect that is what gives them an advantage over normal toroids.

On the other hand, the ones i have tested, have had more mechanical noise than normal toroids.
Click to expand...

Probably caused by loose winding? Normal rectagular shaped cores will put more mechanical stress on the wires when winding through the corners, thus making them more stable. I had to order samples from China because I could not get them here in Taiwan. I was just surprised that the turn on current was much larger than the R-core I tried.

The only time I had problems with mechanical noise was with the traditional transformers. Many people still like them for some reason.
 
W

wtfaidh

Member
Joined 2004
Lars Clausen said:

LM4562: My initial testings show that THD data does not improve with this chip compared to LM6172, which actually has very good THD performance, almost comparable to the best i have tested so far (OPA 627).
However the sound may very well be better on LM4562, but i have until now only made functional tests of sound performance, no A/B tests.
Click to expand...

Hallo Lars,

Nice to hear the first results on the LM4562, but your quote "may very well be better " does that imply that you did not listen to them at all ? e.g. "just" measurement or that you did listen but without a reference ?

Hope to hear your impression on a a/b test on this site soon.

Regards, Eric.
 
W

wtfaidh

Member
Joined 2004
Wish me luck !!!!

Boys will be boys !!! On the brink of 2006 I've just ordered my first set of class-D amplifiers :

- 2 x NCD with LM4562
- 2 x PSU 15.000/6 wire
- 2 x Softstart / filter combo

Now the search for some proper housing/enclosures begins. If all goes well I'll be able to start building somewhere in january 2007.

I am verry, verry, verry curious about this all....

B.T.W. I just listened to a "Musical Fidelity A5 Amplifier". A friend of mine is inclined to buy either this one or a Primare A30. That would be a lovely reference point nah....???

Happy new year to you all (and wish me luck ;-))

Eric.
 
soongsc

soongsc

Member
Joined 2005
One thing I enjoy with this amp is the ability to build in a polarity switch making it very easy to test recording polarity, some of which I find were recorded polarity inversed. I just demonstrated this to a friend a few days ago, and he was amazed with the difference.
 
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